An access structure is needed to enable workmen to have access to the top of bulk material transport vehicles such as bulk material tank trucks used to transport fluid material. In one form of such an access structure, a pair of cantilever arms supporting a service platform are mounted on a pair of upright supports or pillars and are reciprocated up and down by a pair of linear acting fluid actuators. Although fluid may be supplied to the actuators by way of a flow divider, it is possible for the flow to the actuators to be slightly unequal. Thus over time one cantilever arm may be somewhat elevated relative to the other, thereby creating an unsafe, non level service platform and binding in the carriage roller connection between the cantilever arms and the upright supports. It is desired to provide structures which keep a safe inclination and avoid binding in the roller carriage connection. Prior bulk material access platforms have an elongated tank access opening extending along their entire length and a narrow walkway along one side of the elongated opening. Thus platform support for workers was provided only on one side of the opening. It has been found desirable to provide platform support for workers positioned on more than one side of the tank area being serviced.